This R21 application for a 3-year exploratory/development grant for intervention research is designed to develop, standardize and provide a preliminary test of a novel intervention for children, ages 9-11, placed in foster care. Children and adolescents with a history of maltreatment and subsequent placement in foster care are at risk for substantial mental health and behavioral problems of great public health significance. In our prior longitudinal work with children in foster care, we have described the population, examined child welfare system impact, and identified modifiable psychosocial risk and protective factors. These preintervention activities, supported by the Principal Investigator's Career Development Award, have enabled us to address important methodological issues that have hampered the development of intervention efforts targeting this high-risk population. Based on this pre-intervention research, feedback from focus group participants, and a review of other efficacious programs for high-risk youth, we propose to design an intervention for preadolescent youth in foster care consisting of three primary components: assessment, mentoring/advocacy, and therapeutic skills groups. The proposed R21 activities include developing the assessment battery and intervention protocol, manualizing the treatment, estimating recruitment and attrition rates, and conducting a small-scale randomized-controlled pilot study of the intervention. The goals of the intervention will be to improve mental health functioning and academic achievement and to reduce youths' initiation of, and participation in, problem behaviors. We will conduct a preliminary examination of whether these proximal outcomes are moderated by baseline characteristics and/or mediated by the process variables targeted by the intervention. Estimates of effect size will be used to determine the sample size needed for adequate power to conduct a full-scale randomized controlled trial. The pilot study will also focus on issues of feasibility, program uptake, and replicability, and we will modify the assessment battery, protocol, and manuals following the pilot phase and prior to our application for an R01 to conduct a large-scale efficacy trial.